68. Glue Clues From Geckos

A team of biomedical engineers and materials scientists at Northwestern University have invented a glue that behaves like the adhesive on a Post-it note, with the advantage that it also works on wet surfaces. Once out of the lab, it may drive the creation of a host of medical, military, industrial, and consumer products.

Inspired by the sticking strategies of both geckos and mussels, the glue is called Geckel. “We borrowed useful properties of both animals,” says Phillip Messersmith, who announced the findings in June.

Geckos cling to walls and ceilings by means of microscopic hairs on the undersides of their feet. The hairs’ adhesive ability is believed to come from weak molecular-level interactions, called van der Waals forces, between the dry surface and the gecko’s foot—strong enough to counter the gecko’s weight but weak enough that the gecko can easily pull free. The hairs have almost no sticking power under water, however. That’s where mussels come in—the shellfish use an adhesive protein to attach firmly to wet surfaces.

The creators of Geckel used electron-beam lithography to drill nanoscopic holes in a thin polymer film, creating a mold. They filled the holes with liquid silicon and allowed it to solidify; when the film was peeled away, there remained a dense array of tiny pillars much like gecko hairs. When coated with a polymer that mimics the mussel’s adhesive protein, the pillars can stick to wet surfaces. The glue remains sticky in or out of water, even after being pulled away and reattached more than a thousand times.